1. Field of the Invention
The present invention relates to a method of reclaiming a cathodic active material of a lithium ion secondary battery which is used as a power source for various electronics such as videotape recorders and communication tools.
2. Related Art
Nonaqueous electrolytic batteries attract considerable attention as the battery with a high energy density and have come to be widely used as the power source for electronics along with the recent progress of a variety of down-sized and light-weight electronics such as videotape recorders, communication tools and the like. Among these nonaqueous electrolytic batteries, lithium ion secondary batteries, unlike other secondary batteries, do not contain the metal components of which use must be carefully considered from the standpoint of environmental problems, such as mercury, cadmium and lead, and are also characterized by having a sufficient cycle life. Hence the usage of the lithium ion secondary batteries is steadily increasing. As for materials used for the lithium ion secondary batteries, both of materials currently used and materials proposed for the next generation contain rare metals such as cobalt and the like, which are specified as the national stock material. Hence public attention is focused on the recovery of rare metals from used lithium ion secondary batteries to reuse these metals.
In the above-described circumstances, it has been activated in view of conservation of natural resources, to develop the technology for recycling lithium ion secondary batteries, and the target for reclamation is on the metal compounds used as a cathodic active material such as cobalt compounds, lithium compounds, nickel compounds, manganese compounds and the like.
For example, there is a proposed process for recovering cobalt hydroxide, in which the batteries are calcined and crushed, the crushed batteries are screened after iron is removed from the crushed batteries by means of magnetic separation, the minus sieve of the crushed batteries are dissolved in an acid, and solvent extraction is made on the acid solution, thereby obtaining cobalt hydroxide. This process can yield cobalt hydroxide of a relatively high purity as a recovery product.
In the above process, however, an expensive organic agent is used for precipitation and much electric power is also necessary for recovering lithium by electrolysis which is performed separately from the recovery of cobalt. Therefore, this process has a problem in running cost. Moreover, if the recovered materials, cobalt and lithium, are used in preparation of the cathode of batteries, they must be further refined before blending them to make a starting material for production of the carhodic active material. Therefore, it costs much to apply the above recovery process to reclamation and recycle of the active material.
As clearly understood from the above description, the conventional process for recovering cobalt from lithium ion secondary batteries costs much because of the use of expensive organic agent and has a disadvantage that the metal elements from which the cathodic active material is composed, or lithium and cobalt, are separately recovered and an active material such as can be reused is not directly obtained.